Telephone system



Nbv. 19, 1940;

E. WOCHINGER TELEPHONE SYSTEM Filed April 14, 1.938 7 Sheets-Sheet l v3% w vn u N v N w Naming um,

ATTORNEY.

Nov, 19, 1940. E. WOCHINGER TELEPHONE SYSTEM Filed April 14, 1938 7Sheets-Sheet 5 N QNw nl. mm h ow mwu (WNW mw NNv w m \Q INVENTOR. EDUARDWOCHINGER ATTORNEY.

NW. 19, 1940; WQCHINGER 92,222,132

TELEPHONE SYSTEM Filed April 14, 1958 7 Sheets-Sheet 6 w 9 it v D I L o0' a;

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Patented Nov. 19, 1940 UNITED STATES PATENT OFFICE TELEPHONE SYSTEMApplication April 14, 1938, Serial No. 202,099 In Germany April 17, 193724 Claims;

The invention relates to telephone systems in which subscribersbelonging to different groups are able to reach the same connectinglines. The groups of subscribers may differ in that for example thecalling arrangements are diiierent (i. e., with or without callregistering) or the feeding current arrangements for the subscriber maydiffer (local or central battery feeding), or the mode of working (fullyor semi-automatic) may be different or the groups may belong todifferent exchanges.

If for example the difference resides in that the One group containssubscribers with call registering while the other contains subscriberswithout call registering it may happen that when the traific is heavyamong the subscribers with call registering the connecting lines whichbecome free from time to time are immediately seized by othersubscribers using call registering, as a result of this latter feature,while the sub scribers without call registering always find theconnecting lines busy so long as there are any registered calls present,unless they reach the connecting line just during the short period bemtween the release of the connecting line after a previous call and thenew seizure by a registered call. The same dificulty may be experiencedby the operator serving to extend subscribers calls when she wishes todeal with calls for example in the opposite direction. In order to avoidsuch dilficulties the arrangement according to the invention is suchthat switching means in the connecting lines place these exclusively atthe disposal of a calling subscriber of the one group only after havingbeen influenced by a switching operation on the part of an operatorserving the subscribers or after the expiry of a definite period fromthe time of release of the connecting line after a previous call so thatif desired a call outgoing from a subscriber of the other group can bedealt with over the connecting lines before a call outgoing from asubscriber of the first group.

Embodiments of the invention are represented in the Figures 1-7, Figs. 1to 6 serving to explain one embodiment and Fig. '7 a further embodiment.

In detail Figures 1-4 show the circuit arrangements of semi-automaticsubsidiary exchanges Whose calls are set up by means of the switchingmeans shown in Fig. 5 at an operators position in a main exchange HA.Fully automatic subscribers also have access to the semi-automaticnetwork. The general arrangement of the system as a whole is shown inFig. 6. This will be described first.

It can be seen from this figure that the subsidiary exchanges Ul-U4 areconnected in series and have access to a main exchange HA in which thesetting up of calls between the individual subscribers of thesesubsidiary exchanges or to other 5 exchanges can take place. Thearrangement con-- stitutes a semi-automatic system. A fully automaticsystem is also connected to the main exchange HA, the subscribers ofwhich system set up both their internal calls and also their calls tothe individual subsidiary exchanges automatically by means of the usualsetting of switches without making use of the exchange operator.

The circuit arrangements of the individual subsidiary exchanges is suchthat in the exchange UI there is provided a link comprising a callfinder and a final selector. This is connected by way of a connectingline with the exchange U2 in which there is also a finder-connectorlink. Between the exchange U2 and the next exchange U3 there is anotherconnecting line, but in the exchange U3 there are two finder-connectorlinks which are correspondingly connected to the exchange U4 over twoconnecting lines. The exchange U4 like the exchange U3 possesses twofinder-connector links. Two connecting lines, only one of which is shownwith a repeater lead from this exchange to the main exchange HA.

The number of connecting lines and finder links can of course bedifierently chosen in accordance with the traffic to be handled. Ifdesired secondary switches can be arranged between the links andconnecting lines.

The establishment of any call required by a subscriber of thesemi-automatic system is effected, as already stated, by means of theoperator in the main exchange HA, the connecting lines seized by thecalling subscriber insofar as they are in the appropriate trafficdirection being used by the operator for setting up the desiredconnecting path when the call is to a subscriber of the same subsidiaryexchange or group of exchanges. The lines which are not required afterestablishment .of the connecting path are released so as to .beavailable for the establishment of other calls.

If subscriber Tnl, for example, of the exchange Ul makes a call thelatter is extended over the individual connecting lines joining thesubsidiary exchanges to the operator in the main exchange. If theoperator wishes to deal with the call immediately she carries out aswitching measure after having plugged the jack AK which causes the callfinder in the individual exchanges to be set on that connecting lineover which the calling signal passed from exchange to exchange and so tothe operator. By this means it is possible not to have the connectingpath over the said exchanges to the operator blocked as soon as asubscriber initiates a call. In this way the operator if she wants toset up a call herself in the semi-automatic system is not prevented fromdoing so by any call which may have been received. Similarly fullautomatic subscribers can dial into the semi-automatic system whilecalls from subscribers of the semi-automatic system are present providedthat the operator has not yet dealt with these. These two possibilitiesare of special advantage in semi-automatic systems I; in which callsfrom subscribers are registered since after the release of a previouscall other registered calls do not immediately block the connecting pathto the main exchange, 50 that the operator or subscribers of the fullyautomatic system can dial into the semi-automatic system.

The details of these operations will be appreciated from the followingdescription.

Establishment of a call within the semi-automatic system (Figs. 1-6) Theestablishment of a call between subscribers TM and T1 02 of thesubsidiary exchange Ul will first be described. Without taking up hisreceiver subscriber Tni operates his magneto and thereby influencesrelay A over its winding I and the subscribers loop. By closing contactis relay A locks up over windingIIinacircuit whichpasses over: earth,battery, contacts la and 20, Winding II of relay A, resistance Wi2,relay A11. and earth. If the connecting link of the exchange U! is freethe following circuit is set up after relay An has energized in thelocking circuit of relay A: earth, battery, relay Mil, contacts lZhi,lflpi, 9cm, wiper M in the rest position, contact Ian and earth. In thiscircuit relay Mil energizes and inter-alia supplies a battery potentialover contact 321ml to lead at of the connecting line leading to theexchange U2. In consequence the following circuit is completed: earth,battery, contacts 40010, 42171., lead al, (Fig. 2) contacts Mic/Z2 andM3202, winding I of relay A2 and earth. The following circuit is alsocompleted in the exchange Ul (Fig. 1): earth, battery, relay HI,contacts ll lmtl, lilpi, wiper Zw5 of the final selector LWi in the restposition, contact Fan, and earth. Relay Hi locks up by closing contacts8M and lthl. Relay Mil deenergizes through the opening of contact lZhl.Accordingly the circuit for relay A2 passing over the Al lead is alsobroken at contact iZmtl. Relay A2 (Fig. 2) remains energized, however,since it has meanwhile locked up over its winding II in the circuit:earth, battery, winding II of relay A2, contacts 35x12, H3502, WW2 andearth.

If the finder link in exchange U2 is free the following circuit is setup when relay A2 energizes: earth, battery, relay MtZ, contacts [07712,8 mm, 5 E3029, wiper Zw5 of the final selector LWZ in the rest position,contact HM? and earth. Relay M152 energizes in this circuit and sets upthe following circuit by closing contact l43mt2: earth, battery,contacts H020, MSmtZ, lead 112 of the connecting line to the exchange U3(Fig. 3), contacts ld3, 2&203, winding I of relay A3, battery and earth.Relay A3 energizes in this circuit. Meanwhile the following circuit hasbeen set up in the exchange U2 (Fig. 2) through the closing of contactmama: earth, battery, relay H2, contacts ifi9mt2, H5102, lltczil, wiperZw5 of the final selector LW2 in therest position, con-' tact M2 andearth. In this circuit relay H2 energizes and locks up by closingcontacts l08h2 and mm. Relay MtZ is deenergized by the opening ofcontact lEll'hZ so that the circuit for relay A3 is broken at contact li31nt2. Relay A3 does not release because meanwhile it has locked upover its winding II: (Fig. 3) earth, battery, winding II of relay A3,contacts 2ll la3, 28503, 206113, and earth.

If one of the finder links in the exchange U3 is free, for example, thatcomprising the call finder AS3- and the final selector LW3, thefollowing circuit is completed: earth, battery, relay H3, contact2l'lp3, wiper ewl of the setting switch EWS in the rest position,contacts M30353, 2i6a3 and earth. Relay H3 energizes in this circuit andcompletes the following circuit over its contact 263%: earth, battery,contacts 2 13M, 245M, lead at of the connecting line to exchange U4(Fig. 4) contacts 36502 3, 3020s, winding I of relay A4, battery andearth. Relay A l energizes in this circuit. Meanwhile relay Ht has been0perated in exchange U3 over contact 22071.3. It holds relay H3energized over contact 2i lh l. The circuit for relay A l is broken bythe opening of contact 25472 5. Relay A l (Fig. i) holds up, however,over its winding 11 in the circuit: earth, battery, winding II of relayA 3, contacts 384cm, 30504, 386014 and earth.

If one of the links in the exchange U i, for example, that comprisingthe call finder A84 and the final selector LWM is free the followingcircuit is completed: earth, battery, relay H5, contact 3Hlpri, wiperewl of the setting switch EW in the rest position, contacts M30 18, 3mm.and earth. Relay H5 energizes in this circuit and completes thefollowing circuit over its contact 339h5: earth battery, contacts 33%5,$22716, lead at to the main exchange HA (Fig. 5), contacts @0505 and101059, winding I of relay A5 and earth. Relay A5 energizes in thiscircuit. Meanwhile relay H6 has operated in the exchange U l (Fig. 4)through the closing of contact 31971.5 and now holds relay H5 energizedover contact 3i4h6. The energizing circuit for relay A5 is broken by theopening of contact 3 i2h6. Relay A5 (Fig. 5) looks up in the followingcircuit over its winding II: earth, battery, winding II of relay Ati,contacts M 3115, and Mimi and earth. Moreover, the closing of contactil5a5 lights up the call indicating lamp AL at the operators position.

From the above description it will be understood that the call fromsubscriber Tn! is stored in the individual exchanges Ufi-U i and isindicated by the lighting of a lamp at the main exchange HA Without thecall finders ASi-AS i in the individual exchanges having been set. Thusthere is no blocking of the individual lines between the subsidiaryexchanges so that these connectlng lines can be used for example for theestablishment of an incoming call by the operator or by fully automaticsubscribers over the main exchange HA. This will be later described indetail.

Had the finder link of the exchange U! been in use when the subscriberTn! made his call relay Mt! would not have energized since then wiper11/15 of the final selector LWl would have left its normal position andcontacts 9cil and m 1 would be open. The call would only be registeredby delay A remaining energized over winding II in series with relay Anso as to be transmitted'to relay Mil by contact 'iaii when the in thenext exchange U2 and so to extend the call as. already described.

If the link in the exchange U2 (Fig. 2) had been engaged relay Mt2 wouldnot have energized after the energizing of relay A2 since the wiper 1105of the final selector LWZ would have been away from the normal positionand the contacts I I302!) and I H5192 open. The call from the exchangeUi would be registered, however, by the continued energization of relayA2. It would be extended to the next exchange U3 as soon as the linkbecame free. If in the latter exchange the link comprising the callfinder A83 and the final selector LW3 is busy the starting chain isswitched over to the next link through the closing of contact H2030. Thecall initiating impulse then operates on this link. Only if this is alsoengaged no call is initiated at first. The call, however, remainsregistered by the continued energization of relay A3 so that it canbecome effective when a link becomes free and the call can be extendedto the next exchange U4.

Corresponding operations take place in the exchange U l where a call issimilarly switched over to the second link in the event of the linkshown comprising the call finder A54 and the final selector LWd and isregistered (relay A4 held energized) if the second link is busy so thatthe call can be extended to the main exchange HA when a link becomesfree. The call is thus not lost.

If now the operator wishes to deal with a call she inserts her answeringplug A86 in the answering jack AK. Relay C59 is thus energized over:earth, battery, relay C50, jack springs, plug, resistance Wil i andearth. Through the closing of contact 425050 the following circuit isset up: earth, battery, resistance Wilt, contact 425050, relay Hi, andearth. Relay Hi energizes. The Opening of contact ilthl opens thelocking circuit of winding II of relay All and also extinguishes thecall indicating lamp AL. The opening of contact 32th! prevents therepeater Ue from being seized by a group selector GW of the fullyautomatic portion of the system. Meanwhile the following circuit hasbeen completed after the energizing of relay C55): earth, battery,choke-coil DTS, contacts llltyb and M2050, lead a l of the connectingline to the exchange U4 (Pig. 4-), contact B ithe, relay J t and earth.Relay J l energizes in this circuit. Through the closing of contact 349%and the opening of contact 35314 relay CM becomes energized in thefollowing circuit: earth, battery, relay CM], contact 3495M and earth.Relay CM locks up by closing contact 35110 In order to set the callfinder in the exchange U4 the operator now actuates the answering key(AH and A192) and her ringing key R. The following circuit is set up:earth, battery, ringing key R, answering key Abl, plug and jack, contactM205, relay B5, contact ll-5.95 and earth. Relay B energizes in thiscircuit and by closing contact 409795 enables the following circuit tobe set up: earth, battery, choke-coil Drill, contact 409225, lead b t ofthe connecting line to the exchange U4 (Fig. 4), contact ii l ly l,relay E4 and earth. In this circuit relay E4 energizes. The followingcircuit is completed through the closing of contact tilled: earth,battery, rotary magnet DAS4 of the call finder ASA, contact 320M,contact fiilfidas i of the rotary magnet DAS l, contacts 3lle4, 345p,wiper cw'l of the setting switch EWQ in the rest position, contacts 3Hlh5, 3ll1a4 and earth. The rotary magnet DAS l of the call finder A84energizes in this circuit. Through the opening of contact 3l8das4 in theenergizing of the magnet DASfl relay R4 is energized. It breaks theoperating circuit for the rotary magnet DAS4 at contact 320M so that themagnet deenergizes and closes its contact 3l8das4 again. Relay R4 isthus short-circuited and the same operations are repeated. Through theinteraction between the two switching means the call finder AS4 isstepped until it reaches the contact marked over contact 324ml by thecall. The following circuit isnow set up: earth, battery, relay C4,contact 3240M, wiper cs3 of the call finder A34, windings I and II ofrelay P4, contact 32'lh5 and earth. In this circuit relays Pt and C tenergize. The opening of contact (H6104 prevents the further stepping ofthe call finder ASA. The speaking leads are switched through at contacts328324 and 329124, while the seized line is guarded by short circuitingwinding 11 of relay P i at contact 326%. After the opening of contact3li5pt relay I-I5 deenergizes and by opening contact 3lllh5 disconnectsrelay H6. When relay C4 energizes in the testing circuit the lockingcircuit for winding II of relay A4 is broken by the opening of contact30504 and also winding I of relay A4 is disconnected at contact 302(34.The opening of contact 36904 removes the shortcircuit about winding I ofrelay D4. Meanwhile after the setting of the call finder AS4 and theenergizing of relay P4 the following circuit has been set up: earth,battery, relay Q4, wiper as i of the call finder ASfl, wiper 61.03 ofthe setting switch EWG in the rest position, contact 32!;04 and earth.In this circuit relay Q8 energizes so that through the closing ofcontact szr a the following circuit is ,set up: earth, battery, rotarymagnet DLW i of the final selector LW4, contacts 357115, 3567M), 3551948and earth. The final selector takes one step forward. Wiper Zwt of thefinal selector LW4 thus passes on to the contact segment. On theenergizing of the rotary magnet DLlW i, relay I-Itil is energized bycontact 363011111 1 so that the energizing circuit of the rotary magnetDLW t is opened. Through the interaction between relay HM and the rotarymagnet DLWQ the final selector LW i is stepped until Wiper Z205 reachesthe marked contact 9 which is marked over contact 325% and wiper (285 ofthe call finder ASH. As soon as this happens relay I-I lil is heldenergized over: earth, battery, relay H40, wiper Zwfi of the finalselector LW t, contact i, wiper cs5 of the call finder AS 11, contact325ml, and earth. Any further stepping of the final selector LW l isprevented by the continued opening of contact 356MB.

Meanwhile the following circuit has been closed: earth, battery,choke-coil DH, contacts 338%, 331040, 336M, 38lu4, 328M, wiper as! ofthe call finder A34, the a3 lead of the connecting line to the exchangeU3 (Fig. 3), contact 244724, relay J3 and earth.

After the speaking leads have been switched through the followingcircuit is also set up (Fig. l) earth, battery, resistance Wii5,contacts tiled, 334M, 382%, 329103, wiper cs2 of call finder A84, leadD3 of the connecting line to the exchange U3 (Fig. 3), contact Wily-t,relay E3, and earth.

After relay J3 has energized over the a3 lead relay C30 becomesenergized in the exchange U3 (Fig. 3) after contact 2547'3 has beenclosed and.

contact 25173 opened. Relay C30 locks up by closing contact 255030.

Through the energizing of relay E3 over lead b3 the following circuit isclosed: earth, battery, rotary magnet DAS3 of the call finder ASS,contacts 2liir3, 2l9das3 of the rotary magnet DAS3, contacts 2l8e3 and2l'lp3, wiper ew'l of the setting switch EWS in the rest position,contacts 2i i724 and 2l8a3 and earth. In this circuit the rotary magnetDASE of the call finder A83 energizes so that the call finder takes astep forward. The opening of contact 2l9das3 switches on relay R3 whichat contact 2ll5r3 breaks the energizing circuit for the magnet DAS3.Through the closing of contact 2l9das3 when the magnet releases relay R3is caused to deenergize. This inter-action is repeated until theconnecting line seized by the subscriber is found. Then the followingcircuit is set up: earth, battery, relay Ct, contact 223a3, wiper cs3 ofthe call finder A83, windings I and II of relay P3, contact 232723 andearth. In this circuit relays C3 and P3 energize. The opening of contact2l'lp3 prevents any further influencing of the rotary magnet DA83.Moreover the relay H3 releases so that relay I-Ial also releases due tothe opening of contact 229713. The speaking leads are switched throughat contacts 225113 and 227103.

The locking circuit of winding II of relay A3 is broken at contact 20503through the energizing of relay C3 in the testing circuit, and atcontact 2fi'lc3 the short-circuit about winding I .of relay D3 isremoved.

Meanwhile the following switching operations have taken place followingthe energizing of relay P3: at contact 232323 winding II of relay P3 isshort-circuited for guarding purposes; at contact Hip-3 relay Q3 isenergized over: earth, battery, relay Q3, wiper as l of the call finderA83, wiper @103 of the setting switch EW3 in the rest position, contact22lp3 and earth, so that the closing of contact 242 73 completes thefollowing circuit: earth, battery, rotary magnet DLW3 of the finalselector LWS, contacts 249113, 255M353, 2521232 and earth. The finalselector LIP/'3 takes a step forward. Through the closing of contact 2?ldlwS of the final selector LW3 relay H3?) is energized and this breaksthe energizing circuit of the rotary magnet at contact 25lh30. Throughthe inter-action between the rotary magnet DLWB and relay H38 the finalselector is advanced step-wise until wiper Zw5 of the final selector LWSreaches the contact l marked by contact 225113 over wiper as? of thecall finder A83. Over this circuit relay H30 is then held energized sothat any further stepping of the final selector LWZi is prevented by thepermanent opening of contact 25lh3il.

Meanwhile the following circuit is set up over lead at through theclosing of contact 226193 after the energizing of relay P3: earth,battery, chokecoil D75, contacts 23'lu3, 235030, 235703, 228u3, 226103,wiper asl of the call finder A83, lead (12 of the connecting line to theexchange U2 (Fig. 2), contact l l2mt2, relay J2 and earth. Moreoverafter the closing of contact 221123 the following circuit is set up overthe lead b2 1 earth, battery, resistance Willi, contacts 21963, 238703,222113 and 227103, wiper cs2 of the call finder A83, lead b2 of theconnecting line to the exchange U2 (Fig. 2), contact l54y2, relay E2 andearth.

On account of the energizing of relay J2 over lead at the relays C2 andC28 are energized over contact lttjZ.

The energization of relay E2 over lead b2 causes contact l2'le2 to beclosed so that the following circuit is set up: earth, battery, relayH20, contacts l2'9h2, l2'le2, and earth. In this circuit relay H20energizes and by closing its contact l28h20 locks' up. Through theclosing of contact llflhZt the following circuit is set up: earth,battery, rotary magnet DA82 of the call finder, contact l l6r2, contactl I ldas2 of the rotary magnet DASZ, contacts llilh20, H5122, Il4h2,wiper Z205 of the final selector LWZ, contact ll2a2 and earth. In thiscircuit the rotary magnet DAS2 energizes so that the call finder A82takes a step forward. Through the opening of contact llldasZ relay R2energizes in the above circuit and by opening contact ll6r2 disconnectsthe rotary magnet DAS2. The interaction between relay R2 and the rotarymagnet DAS2 causes the call finder A82 to be stepped forward until itreaches the connecting line seized by the calling subscriber. Thefollowing circuit is then set up: earth, battery, relay C2, contactl2tla2, wiper cast of the call finder A82, windings I and II of relayP2, contacts l2 lh2, l25h2il, M61128, contact l2! e2 or l22c2ll or WiperZ106 of the final selector LWZ in the rest position and earth. In thiscircuit relays C2 and P2 energize. Through the opening of contact H5102any further stepping of the call finder A82 is prevented. Through theclosing of contacts l30p2 and l3lp2 the speaking leads are switchedthrough while the high resistance winding II of relay P2 isshort-circuited by the closing of contact 123102. Through the opening ofcontact H5122 relay H2 is deenergized and by the opening .of contactl29h2 relay H20 is deenergized.

On the energizing of relay C2 winding II of relay A2 is disconnected bythe opening of contact M5502 and through the opening of contact lll2c2winding I of relay A2 is disconnected.

Meanwhile through the closing of contact l30p2 the following circuit hasbeen set up: earth, battery, relay X2, contacts l3'lc20, l8lb2, l86u2and l3llp2, wiper asl of the call finder A82, lead al of the connectingline to the exchange UI (Fig. 1), contact llmtl, relay Jl and earth.

Moreover through the closing of contact |3lp2 the following circuit iscompleted: earth, battery, resistance Wi-s, contacts l52h20 or l5l'le2and "HMO, M51112, l35lc2, l34b2, l8'lu2, l3lp2, wiper cs2 of the callfinder A82, lead bl of the connecting line to the exchange Ul (Fig. 1)contact 52yl, relay El and earth.

In the circuit passing over lead al relay J I (Fig. 1) in the exchangeU! and relay X2 (Fig. 2) in the exchange U2 energize. Through theenergizing of relay J I in the exchange Ul contact 5671 is closed, sothat relays Cl and Cl 0 energize. Relay El is energized in the circuitcompleted over the bl lead and by closing contact lflel energizes relayHlfi. Through the closing of contact I lhllJ the following circuit isset up: earth, battery, rotary magnet DASl of the call finder ASI,contacts I61"! and lbda-sl of the rotary magnet DASl, contacts llhlfl,lllpl and thl, wiper Z of the final selector L'Wl in the rest position,contact Ian and earth. In this circuit the rotary magnet energizes,advances the switch one step and energizes relay Rl so that by the wellknown interaction between the two switching means the call finder ASl isstepped till it reaches the called subscribers line. The followingcircuit is then completed: earth, battery, relay C, contact 5a, wipercast of the call finder ASl, windings I and II of relay Pl, contacts25M, 24bit] and 23pm, contacts 20c! or 2 lclll or the wiper lwfi of thefinal selector LWl in the rest position, and earth. In this circuitrelays C and PI energize. Through the opening of contact 20 the lockingcircuit for winding II of relay A and the energizing circuit for relayAn are broken. When relay PI energizes any further stepping of the finalselector AS! is prevented by the opening of contact lllpl. Moreoverrelay I-I! deenergizes and by opening contact 1972i deenergizes relayI-Ilfl. The speaking leads are switched through at contacts 26p| andZlpi, and the high resistance winding II of relay PI is sho-rt-circuitedby the closing of contact 2210!.

If the ringing key It is still depressed, by the operator in the mainexchange HA, battery potential is applied to the b-lead from exchange toexchange so that the corresponding E-relays are still operated. Relay Elenergized in the exchange Ul enables the following circuit to be set upif the calling subscriber has not remained at his station: earth,battery, resistance Wz'l, relay WI, contact Mel and earth. Through theclosing of contact t lwl the subscriber is called back to his station.When he replies after the ringing key has been released and all theE-relays in the subsidiary exchanges have been released, among theserelay El in the exchange Ul, the following circuit is set up: earth,battery, relay XI, contacts tllcill, 2922!, iipl, wiper asl, subscriberTnl, wiper (182, contacts 26121, Mbl M, relay Y5, and earth. The furthertransmission of ringing current is prevented. Over contact 531 and thechoke-coil Drl battery potential is applied to the bi lead and energizesrelay Y2 in the subsidiary exchange U2 which now applies battery to leadbri over contact l53y2 and the choke-coil Dr i.

This influences relay Y3 in the exchange U3 which applies battery tolead b3 over contact Mtg/3 and the choke-coil Drfi. Relay Y4 thereforeenergizes in the exchange U4 and extends battery over lead 114 to themain exchange HA over contact 3431/4 and the choke coil Drt. Since relayBil in the main exchange has released after the restoration of theringing key winding I of relay St is connected up over contact 408195.On account of the closing of contact 4I9s5 the clearing signal lamp SLlights up indicating to the operator that the subscriber has replied.The operator can now make her inquiry.

If the subscriber Tnl wishes to call the subscriber T112 of his ownsubsidiary exchange III, the operator now dials the digitscharacterizing the connecting lines leading to the individual subsidiaryexchanges. Contact nsl is therefore closed impulsively through theoperators dialling while contact nsa remains open throughout eachimpulse train.

The first impulse train may comprise three impulses. Accordingly relayJ5 is energized thrice over contact nsi (Fig. 5). During this time,relay V5 which is slow-to-release is held energized through theintermittent closing of contact 420;)5. Corresponding to the energizingof relay J5 contact lll ly'fi is opened three times so that theenergizing circuit of relay J4 (Fig. 4) which passes over the'lead at ofthe connecting line to the exchange U l is broken three times. In theexchange U l (Fig. 4) relay V4 is connected up on the first release ofrelay J4 over contacts 350% and 3840 and being slow-to-release remainsenergizecl throughout the impulse train. Moreover, the following circuitis closed and broken again corresponding to the impulses transmitted bythe operator: earth, battery, rotary magnet DEW l of the setting switchEW4, contacts 362040, 35874, ittilip lil, and earth. The rotary magnetDEWt is energized three times and thus steps the setting switch EW4 bythree steps. In consequence its wiper ewl stands on the contact alreadyreached by wiper 1104 of the final selector LWt so that since relay Qtwhich is held energized over contact 322124 during the impulsing makes adelayed release after the impulsing and thus maintains its armatureoperated for some time thereafter, the following circuit is set up:earth, battery, windings II and I of relay D4, wiper hail of the finalselector LWA, windings I and II of relay PM, contact 368% (relay V4 isdeenergized after the impulse transmission), contact 3(iliq i,and inparallel therewith over earth, battery, winding III of relay P at,resistance With-wiper Zw l of the final selector LW l, wiper etc! of thesetting switch EW l, contact 370048 and earth. In this circuit relays Diand PM] energize so that the following circuit is also completed beforethe release of the slow relay Q4: earth, battery, relay U4, contacts313%, 311M340, and 319049 and earth. Relay U i now holds up over itscontact illiud while relay PM locks up over its winding III and contact3651040.

It should be mentioned that relay Kt was energized over contact fiiitdewl when the rotary magnet DEWQ of the setting switch energized and thenlocked up over contact i illc t and M61114 of the relay Y i deenergizedby the opening of contact 334164 and wiper ew'ii of the setting switchEVWI which has been moved out of the rest position. Through the closingof contact 335%, relay J3 in the exchange U3 is held energized: afterrelay P tt has energized and the speaking leads have been switchedthrough at contact 37411453 and lil'lp lfl, the locking circuit for thisrelay J3 passes over: earth, battery, relay X4, contacts limit and Eli-pm, wiper Zwi of the final selector LWd, lead all, to the subsidiaryexchange U3 (Fig. 3), contacts 245M, till 2713, relay J3 and earth.

Relay Y l which was previously energized on the calling partys reply anddeenergized after the opening of contact 334M is energized in thefollowing circuit after the final selector LW l has been set since thespeaking leads in the call finder A84 are open at contacts Mint and362ml: (Fig. 3) earth, battery, choke-coil Drli, contact 24(iy3, lead113 of the connecting line of the exchange U4 (Fig. 4) wiper 17.02 ofthe final selector LW i, contact Slfip lll, and 316st, relay Y4 andearth. At contact Mtg/t the locking circuit for relay K t is broken.

By means of a second impulse train which may similarly comprise threeimpulses relay Jli in the main exchange HA and relay J t in thesubsidiary exchange U4- are again energized in a corresponding manner sothat through the intermittent interruption at contact 33km (Fig. 4) thecircuit of relay J3 (Fig. 3) passing over lead ail of the connectingline to the exchange U3 is correspondingly interrupted. In the exchangeU3 relay V3 energizes over contact 3537? on the first release of relay J3 and remains energized on account of its slow-to-release feature duringthe whole impulse train. In addition the following circuit is set up:earth, battery, rotary magnet DEW3 of the setting switch Ewe, contacts262030, 261173 and 2.50pm and earth. The setting switch EWE is advancedthree steps. Relays P30 and U3 are influenced in dependence upon relayQi in a similar manner to that occurring in the case of exchange U i.Moreover, relay K3 has been switched on over contact zfitdewd when thefirst impulse became operative and has locked up over contact 260103 andcontact 2591/3 of the relay Y3 deenergized through the opening ofcontact 230k3. After relays P and US have been energized the followingcircuit for relay J2 in the exchange U2 (Fig. 2) passes over: earth,battery, relay X3, contacts 2397'3 and 2771230, wiper Zwl of the finalselector LW3, lead a2 to the subsidiary exchange U2 (Fig. 2), contactM2mt2, relay J2 and earth. Relay Y3 in the exchange U3, which wasdeenergized by relay K3 on the first impulse because of the opening ofcontact 238703 energizes again over contact 2781030. After the speakingleads have been switched through relay K3 releases on account of theopening of contact 259113.

The next impulse train which can similarly consist of three impulsesoperates in a similar manner on the relay J2 in the exchange U2 (Fig. 2)through the impulsive opening of contact 23973 and there, in addition tothe energizingof the slow-to-release relays V2 and V20 over contactI50y'2, causes the intermittent operation of the rotary magnet DLW2 ofthe final selector LW2 over: earth, battery, rotary magnet DLW2 of thefinal selector LW2, contacts U502, H672 and M31020, and earth. The finalselector LW2 is stepped forward. Through the energizing of 'relay V20relay K2 has been energized meanwhile over: earth, battery, relay K2,contacts W502!) and M3302, and earth, so that when now relays V2 and V20release at the end of the impulse train on account of the opening ofcontact I597'2 the following testing circuit is set up: earth, battery,winding I of relay D2, contacts IIBspZ, and wiper ll'ld2, wiper 11113 ofthe final selector LW2, winding I of relay P20, contacts I85e2, l6Ik2,M8020 and l63c2 and earth. In this circuit relays D2 and P20 energize.Relay D2 serves to guard the connecting line, while relay P20 whichlocks up over its winding III after relay K2 has released at the end ofthe impulse train causes the speaking leads to be switched through atcontacts II8p20 and I'I9p20. In this connection it should be mentionedthat when relay K2 energizes during the dialling, relay B2 is connectedup to the lead bl of the connecting line over contact I33k2 and isenergized over its contact 53'JI and the choke-coil Drl in the exchangeUI so that accordingly the locking circuit for winding III of relay P20at first passes over: earth, battery, winding III of relay P20, contactsI80p20, l68b2 and H5302, and earth. The locking circuit for relay B2passes over contact I34b2 after relay K2 has released at the end of theimpulse train. Since, however, after the energizing of relay P20, relayU2 is energized over: earth, battery, relay U2, contacts l90p20 andI89p2, wiper asd of the call finder A82, wiper Zw I of the finalselector LW2, contact l88c2, and earth, on account of the setting ofselector LW2 on the line seized by the calling subscriber i. e., by thecoincidence between the setting of the call finder AS2 and the finalselector LW2, relay B2 is deenergized now through the opening of contactl01u2. Relay P20 now holds up over its winding III and, contact I9Iu2.After the speaking leads have been switched through the locking circuitfor relay J I in the exchange Ul is as follows: earth, battery, relayX2, contact I397'2 and I18p20, wiper Zwl of the final selector LW2, leadal, in the subsidiary exchange UI, (Fig. 1), contact 4Imtl, relay J Iand earth. Relay Y2, which deenergized on account of the opening ofcontact I357c2 when relay K2 energized is energized again at the end ofthe impulse train and after the speaking leads have been switchedthroughover: (Fig. 1)

earth,'battery, choke-coil Drl, contact 53yl, lead bl, call finder,(Fig. 2), wiper 1202 of the final selector LW2, contacts I'I9p20, I45w2,I5Ih20, and l49e2, relay Y2 and earth.

The next impulse train transmitted by the exchange operator may alsoconsist of three impulses and serves to set the final selector LWI inthe exchange UI on the wanted subscribers line. This impulse train istransmitted over the individual subsidiary exchanges like the precedingimpulse trains and operates in the exchange Ul by influencing relay Jlin a similar manner so that when relay J l first releases an energizingcircuit is produced by relays VI and VII) over contact 517 I. Theserelays remain energized throughout the impulse train through beingslowto-release. The rotary magnet DLWI of the final selector LWI isinfluenced over contact Hi I. On the first impulse moreover relay Kl isenergized over: earth, battery, relay Kl, contacts Hull], and 58cl andearth. Through the closing of contact 327cl relay BI is connected to thelower speaking lead and is energized over the loop of the callingsubscriber Tnl, contacts 29b| and 30cl0, relay XI and battery. Since nowrelay YI is disconnected from the subscribers loop through the openingof contact M it releases and by disconnecting the battery potential overchoke coil Drl at contact 53yl deenergizes relay Y2 in the exchange U2.In a corresponding way the Y-relays at all the other subsidiaryexchanges deenergize so that the clearing signal lamp SL in the mainexchange is extinguished. Through the opening of contact 291)! relay XIwhich was held energized over the calling subscribers 100p releases.

If the wanted subscriber T112 is free the following-circuit isestablished after relay VIO has deenergized at the end of the impulsetrain and before relay KI has deenergized: earth, battery, relay CO,wiper Z103 of the final selector LWI, winding I of relay Pl0, contacts"IQeI, ISkl, 'I6vI0 and 58cl and earth. Relay PIO energizes and locks upover its winding III in a circuit over earth, battery, winding III ofrelay PIO, contacts 62pl0, 63M and 58cl and earth. By depressing theringing key R the operator now causes relay El to be energized in thesubsidiary exchange UI in that the E-relays in the individual exchangesare operated in succession so that over contact Mel relay WI energizesand ringing current can be transmitted to the wanted subscriber T112over the operated contact Mwl. The transmission of ringing current canalso take place automatically. In this case the operation of relay El isnot necessary but instead a five seconds switch is brought intooperation. When the wanted subscriber T112 replies relays XI and YI areinfluenced over his loop during a pause in the ringing so'that now bythe application of a battery potential to the b-lead over the variouscontacts of the Y-relays the clearing signal lamp SL is lit up in themain exchange HA in the same way as has been described above inconnection with the reply of the calling subscriber. The subscribers cannow converse together.

Since the links in the subsidiary exchanges U2, U3, and U4 are notrequired for the conversation between subscribers Tnl and Tn2 they arenow released through the operator withdrawing her plug. Relay C50 in themain exchange first releases so that relay H in the main exchangedeenergizes through the opening of contact 425050 and then releases therepeater Ue (429M). Through the opening ofcontactll02c50 batterypotential is disconnected from lead c4 of the connecting line to theexchange U4 so that relay J4 in the exchange U4 (Fig. 4) deenergizes.Through the closing of contact 35374, relay C40 is short-circuited sothat it releases its armature. In dependence upon the deenergizing ofrelays J4 and 040 the devices in the subsidiary exchange U4 are nowreleased in a manner with which we are not concerned, the final selectorLW4 being first restored to normal and then the setting switch EW4 sothat after the restoration to normal of wiper ewl the link can be seizedafresh. Since on account of the opening of contact 33iy'4 batterypotential is removed from lead at relay J3 in the exchange U3 releaseswith the result that relay C30 deenergizes through the closing ofcontact 25MB. Thus all the devices in the exchange Uii are alsoreleased. Similar switching operations take place through thedeenergizing of relay J2 in the exchange U2 (Fig. 2). First relay V2 isoperated over contact I597? so as to short-circuit relay G2 at contactH5202 so that this relay deenergizes and then also relay C20. The linkin the exchange U2 is then released. In the exchange U-l relay J ldeenergizes through battery being disconnected from lead a! of theconnecting line (Fig. 2: contact H3972). however, in this exchange relayBI is energized over the loop of the calling subscriber 'Inl thefollowing energizing circuit obtains for relay SI: earth, battery, relaySi, contacts 65b5, 84b1, 62pm, 63M, and 580i and earth. Through theclosing of contact tiljl when relay J I releases relay VI energizes butrelay Cl is short-circuited over contact 601)! since contact 59s! isopen, consequently the link in the exchange UI remains set so that theestablished connection is main' tained. In order to guard this linkagainst seizure for example over leads al and bl the following circuitis closed: earth, battery, choke-coil D rl, contact 53yl, lead bl of theconnecting line to the exchange U2 (Fig. 2) relay S172, contactsMiter/Z, W502 and llltcZZ and earth. Relay Sp2 is energized in thiscircuit and while removing the short-circuit from winding II of relay D2at contact M38192 guards the connecting line leading to the exchange UIand thus also the link in the exchange Ui against seizure.

When the conversation between subscribers Tni and T122 is finishedrelays Bl, XI and Yi deenergize when the receiver has been replaced sothat at first through the opening of contacts 6317i and 656i relays SIand PW deenergize. Through the short-circuiting of relay Cl overcontacts 598! and 50M, relay Cl releases and through the opening ofcontact Etcl relay CH3 deenergizes. The further process of the releaseis of no particular interest.

Calls between subscribers of different subsidiary exchanges in thesemi-automatic network can now be set up in a corresponding manner. Inthis case also the connecting path not used for conversation between thetwo subscribers is released by the operator withdrawing the plug.

Establishment of an incoming call If in contrast with the operationsdescribed above the operator wishes to set up an incoming call and notto attend to a call which is received in the main exchange from thesubscriber Tnl she inserts only the answering plug ASt in the jack andswitches over her enquiry switch but does not carry out the actuation ofthe ringing key which is otherwise necessary. Relay C50 is againenergized and by closing contact 402050 Since,

applies a battery potential to lead a4 so that relay J4 in the exchangeU4 is influenced as above. The call finder A84 does not become set sincerelay E4 is not energized. The closing of contact 34974 causes theenergization of relay which looks up over contact 35lc40.

When the operator transmits two impulses by means of her dial switch,relay J4 is intermittently deenergized through the intermediary of relayJ as described above. The rotary magnet DEW l of the setting switch EW4-is operated over contacts 352040 and 35874. Moreover, relay V4 isenergized during the impulse trains. When this relay releases after theimpulse train an automatic impulsing circuit for the rotary magnet DLW4of the final selector LW4 is set up over earth, battery, rotary magnetDLW l, contacts 359%, 36004, wiper ew l of the setting switch EW4, wiperZwB of the final selector LW4, contacts 356MB and 3551040 and earth.When the final selector LW4 has reached the contact marked by wiper ewlof the setting switch EW4 the following circuit is set up assuming thesetting switch to be set on contact 2: earth, contact 310040, wiper ewlof the setting switch EW4, contact 2, contact ttlqt, winding I of relayPthwiper lw3 of the final selector LW4 and over the wanted subscriberscircuit which is not shown, to battery and earth. If the subscriber isfree relay P40 energizes in the known way. The final selector LW4 isbrought to rest through the opening of contact 3551340, the speakingleads are switched through and ringing current is transmitted and isadapted to be disconnected when the wanted subscriber replies in thesame way as was described in connection with the exchange Ul so that thecall to the wanted subscriber is established. The calling impulse of thesubscriber Tnl of the exchange Ul which was described in the previoussection is taken up by relay A4 and which has led to the energizing ofrelays H5 and H0 is rendered inoperative as regards the link AS4/LW4when an incoming call is set up by the operator during the opening ofcontact M3040. After the deenergizing' of relays J 5 and H6 it passes tothe second link ASW/LVV A' (Fig. 6), and the call registering is ofcourse maintained in this case in the exchange U4 It would be differentif the final selector LW4 had not been set by the operator on asubscriber of the exchange U4 but on the connecting line a3/b3 to theexchange U3. In this case the locking circuit of winding II of relay A4would have been disconnected by the energizing of relay D4, so that theregistration of the call in the ex-- change U4 would have beenterminated. In the exchange U3 relay J would have been energized againafter the connecting line had been switched through and would haveenergized relay Gilt so that the calling impulse of subscriber Tni wouldhave been rendered ineffective as regards the link AS3/LW3 by theopening of contact 2 43038]. The registration of the calling impulsewould be main tained, however, by the continued energization of relay A3in the event of the final selector LWft being set on a subscribers line.Alternatively, for example, if the final selector LWS had been set onthe connecting line alt/b2 to the exchange U2 the relay D3 energized inthe testing circuit would have broken the locking circuit of relay A3 atcontact Zih'idt. In this case the registration of the call of thecalling subscriber Tn! in the exchange U2 would be maintained overwinding II of relay A2. If, furthermore, the operator had set the finalselector LW2 on the connectingline al/bl to the exchange Ul relay D2energized in the testing circuit would have terminated'the registrationin the exchange U2 and the call would now be registered only in theexchange Ul The call of subscriber Tnl remains registered as long as ithas not been attended to.

It can thus be seen that a subscribers call remains registered as far asthat subsidiary exchange in which the final selector is no longer set bythe operator on a connecting line to the preceding subsidiary exchangefor the purpose of setting up an incoming call.

In the other exchanges the call becomes operative immediately after theconnecting path has been released without any further measure on thepart of the subscriber in that if for example an incoming call has beenestablished by the operator to a subscriber of the exchange UI thecalling signal is transmitted from subsidiary eX- change to subsidiaryexchange until the main exchange is reached as soon as the call has beenreleased in the manner set out in the previous paragraph.

When'the operator removes the plug all the connecting devices arerestored in a manner which will not be described here in detail. Sincein the exchange Ul, relay A is held energized, relay An is alsoenergized, so that relay Mtl energizes over contact Tom in the exchangeUI and transitorily applies battery potential to the lead at by closingits contact 42mtl so that relay A2 is energized over its winding I inthe subsidiary exchange U2 and locks up over its winding II. Through theclosing of contact 2a?! relay Mt2 is energized in the subsidiaryexchange U2 so that battery is connected transitorily to lead a2 overcontact l43'mt2. Consequently relay A3 energizes in exchange U3 andlocks up over its winding II so that after relay H3 has been operatedbattery potential is applied transitorily to lead a3 over contact 243Mfor the purpose of influencing relay A4 in the exchange U4. This relayalso energizes and locks up over its winding II. Relay H5 is influencedby the closing of contact titled and now by applying battery potentialtransitorily to lead a4 over its contact 33971.5 energizes relay A5in-the main exchange. This locks up over its winding II and lights upthe call indicating lamp AL.

A corresponding repetition of the call initiating impulse would takeplace if the registering of the impulse had been maintained as far asany of the exchanges U2, U3 or U4. All the operations described in thisconnection take place not only in the case of a call from the exchangeUI, but also in the case of calls from the other subsidiary exchanges.Thus after the release of the incoming call and irrespective of whichsubsidiary exchange has had the registration of the call neutralized andirrespective of the particular subsidiary exchange from which the calloriginates, the call initiating impulse is repeated without any actionon the part of the calling subscriber.

Establishment of a call by a fully automatic subscriber over the groupselector GW If a subscriber of the fully automatic system dials into thesemi-automatic system while a call initiating impulse is registered hefirst sets the group selector GW on the repeater Ue. Since the repeaterUe itself is not blocked by a call which is registered the groupselector tests on lead 0. Relay C5 energizes. Through the opening ofcontact 42505 relay C50 energizes. Relay H1 energizes over contacts42405 and 425050 and breaks the locking circuit for relay A5 at contactMM! and disconnects the call indicating lamp AL. Meanwhile batterypotential has been applied to lead a4 to the subsidiary exchange U4 overcontact 452056 so that in this exchange relay J4 energizes and occasionsthe same switching operations-as are brought about when the operatorplugs in. The calling subscriber can now set up a call in a similar wayto the exchange operator since being a fully automatic subscriber he isequipped with a dial switch. He dials into the semi-autornatic system byoperating relay J5 and sets the individual final selectors of thesubsidiary exchanges on the lines leading to the wanted subscriber inthe same way as the operator. The call registration in the individualexchanges is neutralized in the same way as has been described when theoperator sets up an incoming call.

Thus it can be seen that fully automatic subscribers can dial into thesemi-automatic system so long as there are no calls registered whichhave not been attended to by the operator.

When the connection between a fully automatic and a semi-automaticsubscriber is released, this taking place in the same way as when theoperator withdraws the plug, the call initiating impulse is repeated, atthe operators position just as occurs after the release of an incomingcall set up by the operator.

Fig. 7 represents a further embodiment and represents a variation of thecircuit for the call finder ASd provided in the subsidiary exchange U 3,this being here denoted as ASS. Only those parts which are concernedwith the call finder are represented in this figure. The remaining partscorrespond to the circuits shown in Fig. l.

From this figure it will be seen that when the call initiating impulsecomes from the preceding exchange U3 over lead a3 is received relay ABis energized. It looks up over its winding II by closing contact. some.If the link comprising the call finder and final selector is free thefollowing circuit is set up: earth, battery, relay Hi3, contacts 5!i106, wiper ew-l of the setting switch (not shown, compare Fig. 4:),thermo-contact 525ml, contact 51MB and earth. In this circuit relay H8energizes and closes the following circuit at contact EiZhi: earth,battery, resistance Will, contact 5l4das8 of the rotary magnet DASS ofthe call finder ASE, contacts 5i2h8, 5! i116, wiper ewl of the settingswitch, thermocontact 525ml, contact Eiiiafi and earth. In parallel withthe resistance Will in the said circuit there is connected the rotarymagnet DASc of the call finder ASS over contact 51316. The rotary magnetDASS energizes and advances the call finder by one step. Through theopening of contact fil ldasfi during this energization relay R6 isenergized and disconnects the rotary magnet DASB at contact 5|3r6. Bymeans of the interaction between relay R6 and the rotary magnet DASiithe call finder AS6 is advanced by steps until it reaches the callingline.

The following circuit is then set up: earth, battery, relay C6, contact5l5aS, wiper cast of the call finder A56, windings I and II of relay P6,contacts 52'lh8 and 5280481 and earth. In this circuit relays CS and P6energize and bring about switching operations already described inconnection with the corresponding relays in Fig. 4. The difference is inthis case that the following circuit is established through the closingof contact 5l8pt: earth, battery, relay Q4, wiper AS4 of the call finderASE, wiper e103 of the setting switch (shown in Fig. 4) contact 5l8p5and earth. On account of the energizing of relay Q4 at the associatedfinal selector which is connected similarlyto the final selector LW4 inFig. 4 is stepped forward until it has reached the contact characterizedby wiper A35 of the call finder ASS.

Meanwhile a battery potential has been applied to lead a l over contact523106 after the energizingof relay P6 and this brings about theswitching operations in the main exchange HA (Fig. 5) already described.This battery potential is disconnected again after relay Split hasoperated over contact 5|9p6.

The difference between the present arrangement and the call finder AS4in Fig. 4 resides in that the call finder ASS sets itself on the callingline immediately after the reception of the call initiating impulse andconsequently guards this line and moreover brings about a correspondingsetting of the associated final selector which in the case of Fig. 4only takes place in response to an operation on the part of theoperator. Thus there is now no possibility of the link being seized bythe operator for an incoming call or being taken into use by a fullyautomatic subscriber for the purpose of Setting up a call.

The operator in the main exchange now makes her enquiry and sets up theconnection in the manner described above. A separate preparatoryoperation of the ringing key is not necessary. These switchingoperations serve to operate relay C450 (Fig. 4) in the known way, thisremaining energized so long as the connecting link is not used. For thispurpose in Fig. '7 a thermorelay Thl is provided which is connected upover contact 526040 of relay C40. The contact 525th! of the thermo-relaythen breaks the starting circuit for the call finder ASE. Thisconnection has the following significance: When on the re lease of thecall the connecting link is released, whether by the removal of theplugby the operator or after the release of the speaking connection, contact525th! remains open for an interval (for example one minute) so that inthe event of a newly registered call being present this cannot operateimmediately over contact filiiafi. The starting of the call finder ASEand thus the setting and guarding is delayed for a period. During thistime the operator or a fully automatic subscriber has the facility forsetting up an incoming call in a manner which will not be described.Since the setting switch EWt (Fig. 4) is stepped off normal on such acall the calling impulse cannot at first become operative after thecooling down of the thermo-relay Th! and the closing of contact 525th!since then the wiper EW'I (Fig. 7) has left its rest position.Accordingly the release of a connecting device which has been taken intouse is delayed for a period by the thermo-relay so that it cannot betaken into use immediately by a subscriber who has a call registered butinstead although there are calls which have been registered theconnecting device remains for a short period at the disposal of, forexample, fully automatic subscribers or the exchange operator for thepurpose of setting up incoming calls. The arrangement shown in Fig. 7can be applied in any subsidiary exchange in which a thermo-relaydependent upon the corresponding C-rclay and a thermo contact at acorresponding point in the starting circuit is provided. In eachsubsidiary exchange the release of the connecting device after a call isthen delayed for a certain period so that during this time even ifregistered calls are present in the system the exchange operator or afully automatic subscriber can dial into the system. Instead ofinfluencing the thermo-relay over the contact of a C-relay a workingcontact of the call finder ltest relay (P5, Etipli) can be provided inits place. The thermo-relay is then only heated up when a connectiondesired by one of the subscribers of a subsidiary exchange has been setup by the operator but the thermo-relay is not influenced when anincoming connection is established by the operator or a fully automaticsubscriber, in which case the call finder is not set. After such a callthe semi-automatic subscribers have immediate access to the connecting'paths.

What is claimed is:

1. In a telephone system wherein the extension of calls from subscribersstations in a remote exchange is controlled by an operator in a mainexchange over an inter-exchange trunk line, means controlled by asubscriber in the remote exchange for placing a calling condition uponsaid trunk line to notify the operator of his desire to extend a call,means normally operated by the operator in response to the callingcondition on said trunk line to extend a connection over said trunk lineto the calling subscribers line, and means operated at times before saidoperation of said last means by the operator to extend one or more othercalls over said trunk line irrespective of the calling conditionthereupon.

2. In a telephone system wherein two exchanges are joined by a trunkline over which calls may be extended in either direction, and whereinthe extension of local calls in one of the exchanges is controlled oversaid trunk line by an operator in the other exchange, means operable bya subscriber in said one exchange to place a calling condition upon thetrunk line thereby to notify the operator of his desire to extend acall, means normally operated by the operator in response to the callingcondition on said trunk line to seize said trunk line and make samebusy, and means for extending other calls over said trunk line after thecalling condition has been placed thereupon but before said trunk linehas. been made busy by the operation of said last means.

3. In a telephone system, a two-way trunk line, means rendered effectiveby the extension of a call over said trunk line in one direction toprevent another call from being extended over the trunk line in the samedirection within a predetermined interval of time after the terminationof said first call, and means for extending a call over said trunk linein the other direction during said interval of time.

4. In a telephone system, a two-way trunk line, means for storing callsif the trunk line is engaged, whereby calls in one direction over saidtrunk line are held in waiting until the trunk line becomes free, andmeans for placing said trunk line exclusively at the disposal of callsin the opposite direction for a predetermined interval of time after thetrunk line becomes free thereby to prevent said waiting calls frommonopolizing the use of said trunk line.

5. A telephone system as claimed in claim 4, wherein said last means iseffective only when the call in which said trunk line is engaged is acall in said one direction.

6. In a telephone system wherein the extension of local calls betweensubscribers in a remote exchange is controlled by an operator in a mainexchange over an inter-exchange trunk which is released after a localcall has been extended, and wherein inter-exchange calls to or fromsubscribers in said remote exchange are also extended over said trunkline which is released upon the completion of said inter-exchange calls,means for placing said trunk line exclusively at the disposal of callsincoming to subscribers in the remote exchange for a predeterminedinterval of time after each release of the trunk line.

7. In a telephone system wherein the extension of local calls betweensubscribers in a remote exchange is controlled by an operator in a mainexchange over an inter-exchange trunk which is released after a localcall has been extended, and wherein inter-exchange calls to or fromsubscribers in said remote exchange are also extended over said trunkline which is released upon the completion of said inter-exchange calls,means for placing said trunk line exclusively at the disposal of callsincoming to subscribers in the remote exchange for a predeterminedinterval of time after each release of the trunk line following the useof the same in calls originated in said remote exchange, said last meansbeing ineffective when said trunk line is used in an incoming call.

8. In a telephone system, a plurality of exchanges connected in seriesby trunk lines, the exchange terminating said series comprising a mainexchange at which the extension of calls involving subscribers at theother exchanges is controlled, an operators position at the mainexchange, means responsive to the origination of a call at one of theexchanges for registering said call at said operators position, saidlast means including means for registering said call at the originatingexchange and at each ex- A change intervening between the originatingexchange and the main exchange, said registration being thereby advancedto the main exchange over a route including a plurality of said trunklines in series, and means for causing said registration of the call torecede from said main exchange to one of said intervening exchanges orto said originating exchange thereby to permit any desired portion ofthe route over which said registration was advanced to the main exchangeto be used for another purpose.

9. A telephone system as claimed in claim 8, wherein, responsive to therelease of the trunk lines in said portion of said route after the usethereof for said other purpose, said registration is again automaticallyadvanced to said operators position.

10. In a telephone system wherein the extension of calls betweensubscribers lines is controlled by a remote operator over a trunk linecommon to said lines, means responsive to one of said lines initiating acall for placing a calling condition on said common trunk line to signalthe operator of the initiation 01 a call, said common trunk lineremaining idle in response to the operation of said means to enable theoperator to extend a different call over said trunk line to a called oneof said lines.

11. In a telephone system, a plurality of exchanges connected in seriesby trunk lines, the exchange terminating said series comprising a mainexchange at which the extension of all calls between subscribers linesis controlled, an

. operators position at the main exchange, means ators position, saidregistering means including means for placing a calling condition on thetrunk lines intervening between the originating and main exchanges, saidregistering means being ineffective to make said trunk lines busywhereby said trunk lines may be used for extending calls to calledsubscribers lines.

12. In a telephone system, a local exchange, subscribers linesterminating in said exchange a finder and connector switch link in saidexchange for completing connections to and from said subscribers lines,a control trunk extending from said local exchange to a remote operator,means for signalling the operator over said control trunk in response toa local subscriber initiating a call, said finder and connector switchesin said link remaining idle and in unoperated positions during suchsignalling operation, means responsive only to said operator answeringsaid call for operating said finder switch to find the calling line, andmeans controlled at times before the operator answers said call foroperating said connector switch to extend another call to one of saidlocal subscribers lines.

13. In a telephone system wherein an operator at a main exchange remotefrom a local exchange controls automatic switches in the local exchangeover a common control trunk to complete connections between localsubscribers lines, means responsive to the initiation of a call by alocal subscriber for automatically signalling the operator over saidcontrol trunk, said means being effective only in case said controltrunk is idle and also efiective to maintain said control trunkavailable to the operator for completing other calls.

14. In a telephone system, a local exchange, a finder and a connectorswitch link in said exchange, subscribers lines terminating in the banksof said finder and connector switches of said link, a control trunkextending from said link to a remote operator, arelay individual to eachsubscribers line, means responsive to one of said lines initiating acall for energizing and locking the corresponding individual relay inenergized position to register a call, means common to said linesoperated in response to the operation of said relay for signalling theremote operator over said control trunk, said finder switch of said linkunoperated in response to the operation of said last means and said linkremaining idle to enable the operator to use the connector switch ofsaid link to complete other calls.

15. In a telephone system wherein the extension of calls fromsubscribers lines in a local exchange is controlled by an operator at adistant exchange over a trunk line common to said subscribers lines,means responsive to one of said subscribers initiating a call forregistering said call and signalling the operator over said trunk line,means for extending another call over said trunk line after saidsignalling of the operator but before the operator responds thereto,said first means maintaining said first call registered during theextension of said other call.

16. In a telephone system wherein the extension of calls fromsubscribers lines in a local exchange is controlled by an operator at adistant exchange over a trunk line common to said subscribers lines,means responsive to one of said subscribers initiating a call forregistering said call in the local exchange, means controlled by saidlast means over said trunk line for registering said call in the distantexchange, means for thereafter extending another call over said trunkline, means controlled by said last means for cancelling theregistration of said first call in the distant exchange during saidother call, said first means maintaining said first call registered insaid local exchange throughout said other call.

17. In a telephone system wherein the extension of calls fromsubscribers lines in a local exchange is controlled by an operator at adistant exchange over a trunk line common to said subscribers lines,means responsive to one of said subscribers initiating a call forregistering said call in the local exchange, means controlled by saidlast means over said trunk line for registering said call in the distantexchange, means for thereafter extending another call over said trunkline, means thereupon .controlled by said last means for cancelling theregistration of said first call in the distant exchange, said firstmeans maintaining said first call registered during the time said trunkline is engaged in said other call and efiective responsive to samebecoming idle upon termination of said other call to control said secondmeans to again register said first call in said distant exchange.

18. In a telephone system, an automatic exchange, a semi-automaticexchange, subscribers lines terminating in each of said exchanges, aremote operators position for controlling the extension of all callsinitiated by subscribers in the semi-automatic exchange, trunk linesextending from said semi-automatic exchange to said position, switchingmeans in said automatic exchange having access to said trunk lines forthe extension of calls from subscribers lines in said automatic exchangeto subscribers lines in said semi-automatic exchange, means forcontrolling said switching means over a calling one of the subscriberslines in said automatic exchange to test for and select an idle one ofsaid trunk lines, means in said semi-automatic exchange thereaftercontrolled over said one trunk line to extend a connection from said onetrunk line to a wanted subscribers line, means responsive to theinitiation of a call by a subscriber in the semiautomatic exchange forsignalling the operator's position over an idle one of said trunk lines,said means causing said last trunk line to test idle to the switchingmeans in said automatic exchange during such signalling to enable thattrunk line to be selected for a call from said automatic exchange tosaid semi-automatic exchange.

19. In a telephone system as claimed in claim 18, means responsive tothe operator answering said signalling for causing the trunk line totest busy to the switching means in said automatic exchange thereby toprevent that trunk from being selected for a call from said automaticexchange to said semi-automatic exchange.

20. In a telephone system, a group of subscribers lines, a group oftrunk lines accessible to said subscribers lines for the extension ofcalls therefrom, switching apparatus common to said subscribers linesand controlled over a calling one thereof at times to search for andseize an idle one of said trunk lines, a second group of subscriberslines having access to said trunk lines, an operators'position forcontrolling the extension of all calls from subscribers lines of saidsecond group, means responsive to the initiation of a call by asubscriber of said second group for placing a calling condition on anidle one of said trunk lines to notify the operator of the subscribersdesire to extend a call, said last means efiective to maintain said onetrunk line idle irrespective. of the calling condition thereon to permitthe seizure of said one trunk line by said switching apparatus for acall from one of the subscribers lines of said first group.

21. In a telephone system, a group of trunk lines, a switch havingaccess thereto, means for at times operating said switch to search forand seize an idle one of said trunk lines, a group of subscribers linesalso having access to said trunk lines, an operators position forcontrolling the extension of all calls from said subscribers lines,means responsive to the initiation of a call by one of said subscribersfor placing a calling condition on an idle one of said trunk lines tonotify the operator of the subscribers desire to extend a call, saidlast means maintaining said one trunk line idle to permit its seizure bysaid switch despite the calling condition thereupon.

22. In a telephone system, a two-way trunk line, means for extending aconnection over said trunk line, means effective upon the release ofsaid connection to prevent another connection from being extended oversaid trunk line in a particular direction for a predetermined intervalof time after the release of said first connection, and means forextending a connection over said trunk line in the opposite directionduring said interval.

23. In a telephone system, a plurality of groups of lines, a lineaccessible in common to said last lines, means for extending aconnection over said common line from any of the lines in one of saidgroups, means controlled by the release of said connection forpreventing the extension of another connection over said common linefrom any line in said one group for a predetermined period of time, andmeans for extending a connection over said common line from any line ofanother of said groups during said period.

24. In a telephone system, a plurality of groups of subscribers lines, atrunk line common to said subscribers lines, means for extending aconnection from one of said subscribers lines over said trunk line, andmeans controlled by the release of said connection for preventing theextension of another connection over said trunk line from any of thesubscribers lines in the same group as said one line for a predeterminedperiod of time.

EDUARD WOCHINGER.

